Ancillary (or spectator) ligand-metal coordination complexes (e.g., organometallic complexes) and compositions are useful as catalysts, additives, stoichiometric reagents, monomers, solid-state precursors, therapeutic reagents and drugs. Ancillary ligand-metal coordination complexes of this type can be prepared by combining an ancillary ligand with a suitable metal compound or metal precursor in a suitable solvent at a suitable temperature. The ancillary ligand contains functional groups that bind to the metal center(s), remain associated with the metal center(s), and therefore provide an opportunity to modify the steric, electronic and chemical properties of the active metal center(s) of the complex.
Certain known ancillary ligand-metal complexes and compositions are catalysts for reactions such as oxidation, reduction, hydrogenation, hydrosilylation, hydrocyanation, hydroformylation, polymerization, carbonylation, isomerization, metathesis, carbon-hydrogen activation, carbon-halogen activation, cross-coupling, Friedel-Crafts acylation and alkylation, hydration, dimerization, trimerization, oligomerization, Diels-Alder reactions and other transformations.
One example of the use of these types of ancillary ligand-metal complexes and compositions is in the field of polymerization catalysis. In connection with single site catalysis, the ancillary ligand typically offers opportunities to modify the electronic and/or steric environment surrounding an active metal center. This allows the ancillary ligand to assist in the creation of possibly different polymers. Group 4 metallocene based single site catalysts are generally known for polymerization reactions. See, generally, “Chemistry of Cationic Dicyclopentadienyl Group 4 Metal-Alkyl Complexes”, Jordan, Adv. Organometallic Chem., 1991, Vol. 32, pp. 325-153 and the references therein, all of which is incorporated herein by reference.
One application for metallocene catalysts is producing isotactic polypropylene. An extensive body of scientific literature examines catalyst structures, mechanism and polymers prepared by metallocene catalysts. See, e.g., Resconi et al., “Selectivity in Propene Polymerization with Metallocene Catalysts,” Chem. Rev. 2000, 100, 1253-1345 and G. W. Coates, “Precise Control of Polyolefin Stereochemistry Using Single-Site Metal Catalysts,” Chem. Rev. 2000, 100, 1223-1252 and the references sited in these review articles. Isotactic polypropylene has historically been produced with heterogeneous catalysts that may be described as a catalyst on a solid support (e.g., titanium tetrachloride and aluminum alkyls on magnesium dichloride). This process typically uses hydrogen to control the molecular weight and electron-donor compounds to control the isotacticity. See also EP 0 622 380, EP 0 292 134 and U.S. Pat. Nos. 4,971,936, 5,093,415, 4,297,465, 5,385,993 and 6,239,236.
Given the extensive research activities with respect to metallocene catalysts, there is continued interested in the next generation of non-cyclopentadienyl ligands for olefin polymerization catalysts providing attractive alternatives. See, e.g., “The Search for New-Generation Olefin Polymerization Catalysts: Life beyond Metallocenes”, Gibson, et al., Angew. Chem. Int. Ed., 1999, vol. 38, pp. 428-447; Organometallics 1999, 18, pp. 3649-3670 and “Advances in Non-Metallocene Olefin polymerization Catalysts”, Gibson, et al., Chem. Rev. 2003, 103, 283-315. Recently, for isotactic polypropylene, bis-amide catalysts have been disclosed in U.S. Pat. No. 5,318,935 and amidinate catalysts have been disclosed in WO 99/05186. See also U.S. Pat. No. 6,214,939 for non-metallocene isotactic polypropylene catalysts.
Isotactic polypropylene and its production has been extensively studied. See, e.g., U.S. Pat. No. 6,262,199 for isotactic polypropylene produced with metallocene catalysts. In general, those of skill in the art have concentrated on C2 symmetrical metal complexes based on the theory that such symmetry allows for tacticity control. See, e.g., “Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts”, Brintzinger, et al., Angew. Chem. Int. Ed. Engl., 1995, Vol. 34, pp. 1143-1170. For example, Kol et al., J. Am. Chem. Soc. 2000, 122, 10706-10707 and WO 02/36638 disclose a C2-symmetrical structure that may induce tacticity control. However, the art still fails to provide a higher molecular-weight, narrow polydispersity, isotactic polypropylene with a high melting point, in part provided by an isotactic polypropylene having few, if any, regio-errors (or regio-irregularities), produced at high temperatures (e.g., greater than 100° C.) that is commercially desirable.
Therefore, a need exists for the discovery and optimization of non-cyclopentadienyl based catalysts for olefin polymerization, and in particular for certain polymers, such as isotactic polypropylene and ethylene-alpha-olefin copolymers. Furthermore, a need still exists for new catalysts to produce high molecular weight isotactic polypropylene with a high melting point, particularly in a solution process and at higher polymerization temperatures.